Weekly Weather: A warm up, then a front, then another stellar weekend

Good morning and welcome to my weekly weather report on the immediate past, present and future of weather in the Bayou City.

PAST

The greater Houston region, for the first time since last August, is having a month with more rainfall than normal.

But are areas in the worst drought getting the most rainfall? Let’s start off by looking at a map of “percent of normal” rainfall for southeast Texas:

Percent of normal rainfall in southeast Texas since April 1. Click to enlarge. (NOAA)

As you can see Harris County has done quite well, getting 150 to 300 percent of its normal rainfall since the beginning of April, and areas to our east have gotten very much rain indeed. But what is moderately concerning is that the band of heavy rainfall (blue and purple) to the city’s west is relatively narrow. Did it hit the driest areas?

To find out let’s take a look at the most recent drought monitor report, from last Thursday.

U.S. Drought Monitor report released last Thursday. (US Drought Monitor)

What I like about this month’s rains for our area is that they have, to some degree, aligned nicely with the corridor of extreme drought to the west of the city of Houston. Our drought is far from over, but about a month ago I said we would need showers in April and May to help stave off a bad drought this summer. So far we’ve been getting them.

Anyway, let’s do the numbers for last week.

Date

High T

Low T

Average

Departure

Rainfall

Monday

81

67

74

+6

0.00

Tuesday

82

69

76

+8

0.00

Wednesday

83

48

66

-2

0.23

Thursday

69

43

56

-12

0.69

Friday

79

46

63

-6

0.00

Saturday

79

51

65

-4

0.00

Sunday

83

55

69

0

0.00

Average

79.4

54.1

67.0

-1.4

0.92

A similar pattern will occur during the coming week, with a warm start and a cooler weekend.

Already this morning — whereas low temperatures from last Wednesday through Sunday were in the 40s and 50s — we’re seeing lows not fall much further than 70 degrees. Clearly, then, a southerly flow has reestablished itself off the Gulf of Mexico.

Daytime temperatures should warm into the mid- to upper-80s during the first half of the workweek under the influence of this warmer air, and overtime lows through Wednesday night should remain at a sticky 70 degrees.

The main event this week will the the passage of a cool front, say forecasters with the Houston/Galveston office of the National Weather Service.

As of now it appears the front will move through central Houston during the midday hours of Thursday, and be off the coast by evening. It also appears likely a line of storms — possibly severe — will move ahead of the front.

Five-day rainfall accumulation forecast. (NOAA)

The front may bring perhaps one-half inch of rain to Houston, but if some forecast models are correct about atmospheric moisture levels that total may have to be ratcheted up.

Temperatures in the wake of the front will cool considerably, with Friday night’s low falling into the mid-40s, and daytime highs in the 70s for the weekend. Yes, it looks like Houston is in store for yet another beautiful, mild and sunny weekend. Don’t take these for granted, folks.

FUTURE

Last week I wrote about seasonal forecasts calling for a significantly more active than normal Atlantic hurricane season.

But will Texas be affected?

According to forecasts made by Colorado State University’s Phil Klotzbach, the probability of Texas being hit by a hurricane this year is 50 percent, which is above climatology, which suggests that in any given year the chance of Texas being hit by a hurricane is 33 percent.

The chance of a major hurricane, category 3 or larger, striking Texas is 20 percent, above the climatology figure of 12 percent.

I don’t have an overwhelming amount of faith in such forecasts, but that doesn’t mean you shouldn’t get ready for the June 1 beginning of hurricane season.

SUMMARY

My rating scale for this week’s weather goes from 0 to 400, the number of toilets that broke down Friday during the seven-day Caribbean cruise, officials with Carnival Cruise Lines said.

My number: 380.

Finally, if you want several daily updates on weather, please “like” my SciGuy Facebook page. It’s the best place for multiple daily updates on our weather, delivered right to your news feed.

FINE PRINT

As always, thank you to the fine professionals at the National Weather Service for the information and data that make this weekly blog entry possible. Also, bear in mind there’s always uncertainty in weather forecasting, particularly the timing and intensity of precipitation.

Eric, I really appreciate your weekly weather summary. We have not seen the graphic you occasionally post showing the daily high and low temperatures versus the bands of average high and lows. Where is it available on the web? Besides Houston, it would be interesting to look at the plots for other cities and of a national average. I would not expect you to publish those, but would like to see them for myself.

According to forecasts made by Colorado State University’s Phil Klotzbach, the probability of Texas being hit by a hurricane this year is 50 percent, which is above climatology, which suggests that in any given year the chance of Texas being hit by a hurricane is 33 percent.

Holy freakin’ crap. I wonder what the confidence limits are on their predictions?

On the bright side, perhaps this will mollify those who complain that the annual forecasts don’t tell them where the hurricanes will hit.

Thanks for the link, Eric. It appears that they are using a Poisson regression for the “climatological” and scaling it by the “predicted Net Tropical Cyclone Activity” for the annual prediction. Basically, they are saying that on average, Texas gets hit by a hurricane every three years but this is going to be a busy year so we have a fifty-fifty chance.

I’ll give them the Poisson regression; it has a long and strong history in this sort of calculation. But the scaling is a little weaselly, as the probabilities for getting hit by a hurricane might sum to more than one. And it is uncharacteristically dumb (in the mathematical sense) as it is agnostic as to local factors associated with hurricane formation.

John is right. The probability favors Matagorda and Brazoria counties for landfall. But this is purely statistical. If one looks at the hurricane likelihood maps that Eric has published on this blog, they strongly favor the eastern side of the Mississippi and even the Atlantic coast, not the central part of the Texas coast.

My drafty no insulation old house hovers around the lower to mid 60s when I have the heat on. The house has no ducts. Switching to electric heat would be an expensive change, and electric heat costs more. And it is probably even worse for the environment, although I have been buying wind generated electricity for the past few years.

Weather’s going to be great, but given the recent rains following drought, we should launch an official SciGuy betting pool on how many days remain until the peak of the first big mosquito wave of the season. Having absolutely no expertise on this subject, my SWAG is April 19 for north Galveston County.

Tornadoes, tornadoes, tornadoes.
I expect an active tornado season, east of a line from Waco, Texas
through Wichita, Kansas. And east of a line from Monroe, LA through St. Louis;
bad, bad, and bad.
FO-takes your tree.
F1-takes the shingles off roof. Push trailer house.

F2-takes roof. Push trailer house into mouth and eats.
F3-takes house and turns it into a small pile of rubble in a small area.
Lifts car off ground. No more trailer house.
F4-takes the small pile of rubble and scatters it over a large area.
Lifts car off ground and throw a little ways. No more trailer house.
F5-No house. Leave concrete slab where house used to be.
Lifts car off ground and throw a long ways. No more trailer house.

Eric,
If i am reading it correctly, the graphic from Weather Bell shows a higer ACE is the eastern Gulf and along the Atlantic seabord which would make me think that the probability for Texas is neutral or average. But the Colorado State guys are predicting a higher than average chance of a TX hit? What’s the difference between the two predictions?

“I don’t have an overwhelming amount of faith in such forecasts”…Atta boy Eric. I knew you would join my posse sooner or later. Now cinch up your saddle and always remember, don’t drink downstream from the herd.

We have GOT to make corrections here. First, adjacent Chambers Co. is definitely part of the “Houston Region”, but the abundant rainfall has been commonly ignored. Statements like: “The greater Houston region, for the first time since last August, is having a month with more rainfall than normal.” is incorrect. Chambers, IN the Houston Region, is about 5″ ABOVE normal……Also, the Texas Drought Monitor map is WRONG. Overly wet Chambers Co. is solidly yellow, indicating “DO -abnormally dry”. This has been wrong all year.

I saw/read recently in the media that the Atlantic temps were cooler than normal and would translate into a low hurricane season, except for the NW Gulf which is warmer than the rest of the waters surrounding it. They seemed to think any activity would be in our neck of the woods. Can you comment on this?

The maps I’ve seen indicate temperatures in the tropical Atlantic where storms form are 1-2 degrees C above normal (see this map, for example).

My view is that forecasts made in April of where storms are most likely to affect the United States in August or September are to be taken with a large grain of salt. The fact of the matter is that hurricane science has not progressed to the point that such predictions can be made with anything approaching scientific rigor. They’re educated guesses, at best.

Actually, what NWS says is that the severe threat is in central texas. Take a look:

“A cold front will move through southeast Texas on Thursday bringing a chance for showers and thunderstorms. Some thunderstorms could be strong to severe, mainly across central Texas. Much cooler temperatures can be expected behind the front with highs on Friday in the upper 60s to near 70.”

Cap will likely arode across NORTHERN part of town, but, I think areas south of I-10 should be safe. What do you think?